IT TOOK Olney Theater board member Jim Petosa "a month of craziness" to do it, but he has pulled off quite a dramatic coup for the summer theater. British actor extraordinaire Ian McKellen will bring his one-man "Acting Shakespeare" show to the Olney June 30 through July 26. The McKellen program will replace "Amadeus."

"We had originally planned to do 'Amadeus,' in part for the importance of the play," says Petosa. "But we were also looking for a performance of stature -- either a 'name' or a non-name who would give us an amazing, attention-getting performance. In one of our meetings, {National Theater general manager and Olney board member} Harry Teeter jokingly said, 'Why don't we get Ian McKellen to recreate Salieri?' {McKellen originated the role in London}. Then he said 'Wait a minute -- I don't think he's busy right now.' As it turned out, Ian -- who did the show at the National Theater for three months in March -- was really taken with the idea of coming back to Washington."

McKellen's visit "puts us in a different league than we're used to operating in," says Olney spokeswoman Melissa Collins. "But this theater lends itself beautifully to his kind of show -- it's so relaxed and informal." Petosa says McKellen will be staying at the Olney's actors residence, a big white farmhouse next to the theater. "All the young actors are climbing the walls with excitement."

Doctor's orders: After hearing his doctor's warning about exhaustion and a pre-ulcerous condition, actor/playwright T.J. Edwards withdrew from the the cast of "As Is" at the Studio Theater. Edwards has been replaced by Michael Wells, who had a lead role in the "Slab Boys" trilogy at Studio.

Edwards has had a full plate of late: Along with playing one of the leads in "As Is" and working in his rent-paying position as a waiter at American Cafe on Capitol Hill, Edwards has been readying his own new play, "National Defense" for its June 17 opening at Woolly Mammoth Theater; his "New York Mets," which recently won the Helen Hayes Award for best new play, was part of Woolly Mammoth's successful three-play repertory season last year. "As Is," meanwhile, has been extended through July 19.

Dream On: The globetrotting musical "Dreamgirls," which plays the Warner Theater next Wednesday through June 14, comes to Washington fresh from five weeks in Paris. Before that, the flashy Michael Bennett-directed show about a Supremes-style pop-soul trio broke house records during its seven-week stand in Tokyo, where the very American lyrics were simultaneously translated over headphones. The Warner company is the same one that played the National last spring. After Washington, "Dreamgirls" returns to Broadway for a limited run at the Ambassador Theater.

New Kids in Town: Get ready to welcome the Potomac Theater Project, which is moving into the area this summer. Formerly known as the New York Theater Studio, the 10-year-old troupe will introduce itself in August at the Castle Arts Center with repertory of Howard Barker's "No End of Blame" and Daniel Berrigan's "Trial of the Catonsville Nine."

"In a sense, it's a homecoming," says Cheryl Faraone, who shares the directing with James Petosa and Richard Romagnoli. All re graduates of Catholic University and have worked with most of the area's theaters. "We became increasingly dissatisfied with producing conditions in New York," says Faraone, explaining the relocation. "A lot of it had to do with real estate, and what we perceived as a dwindling audience for serious theater. And Washington seems to be a burgeoning city for the arts."

After its summer residency at the Castle, the troupe will have to face up to Washington real estate realities when looking for a permanent home. The Potomac Theater Project will operate under the terms of a Small Professional Theater contract with Actors Equity Association. Call 277-6121.

Bulletin Board: A big-bucks, Broadway-bound revival of "Cabaret" opens a four-week run at the Kennedy Center Opera House September 9. Joel Grey will reprise his role as the M.C.; Alyson Reed is cast as divinely decadent Sally Bowles . . . And "Tango Argentino," which played the Warner last fall, comes to the Kennedy Center Opera House July 8 through 18; the "Tango" team's new show "Flamenco Puro" stamps into the Warner November 10 . . . Worthy Cause Dep't.: Smallbeer Theater Company's Monday night benefit for Ernie Joselovitz's Playwrights Unit will feature a cash-bar reception and staged readings of "Advice to the Players" and "The Love Talker," two intriguing one-acts developed at the Unit. It's at New Playwrights' Theater at 7, minimum donation $10. Call 667-3623 . . . The Javarama, which, we are told, is "patron to the arts of the imagination and serves coffee," is presenting "Love: A Festival of Innocence and Experience," Friday and Saturday, starting at 9:30 p.m. You name it, they got it: poetry, storytelling, synthesizer sampling, reggae and ritual. The out-there event will cost you four bucks. Call 797-7262 . . . Free performances of the original docudrama "Quilting" (not to be confused with the musical "Quilters") will be given Saturday (8 p.m.) and Sunday (3 p.m.) at the Hall of Musical Instruments at the National Museum of American History. Written by Eleanor Traylor, "Quilting" is a patchwork of 18th-century writings about the early U.S. from African-Americans, European settlers and Native Americans, and it's part of the museum's "American Sampler Festival." Call 357-4176 for reservations . . . Theater bargain of the week: comic magicians Penn & Teller are selling their "Mofo Knows" T-shirts at two for $10. The performers themselves hawk the shirts (which are an inside joke for those who have seen the show) in the Center Stage lobby after the performance . . .